Stable beetle per 100 meters
Below is the design of a radio transmitting device with a range of up to 100 meters. Such a radio is built according to the capacitive three-point scheme (as well as all other known schemes), the components were carefully selected. Frequency does not float, as it happens in many schemes of radio-tines. If you stand with the receiver at a distance of 1, 10 and 50 meters from the beetle, then the frequency drift will be only 100-120 kHz - which you agree very little and cannot affect the quality of the wiretapping.Beetle can be used for the purpose of eavesdropping on premises and even objects in motion! This was made possible by selecting the components of the transmitter, which makes the modulated signal fairly stable, and the circuit remains simple and accessible even to a beginner amateur. The transmitter can use RF and microwave transistors of low power. It is desirable to use transistors with a boundary frequency of 700-1000 MHz. Domestic KT368 (which is a complete analogue of the transistor specified in the circuit) is perfect. To increase the sensitivity of the radio microphone, an additional microphone amplifier was used, the circuit of which is built on just one transistor. Transistor is literally any low-power one - КТ3102, КТ315, КТ368, С9014, С9018 and others. Such an amplifier makes it possible to catch even a quiet whisper in a 4x4 meter room. The sensitivity of the bug is about 5 meters. Antenna - stranded wire in rubber insulation with a length of 10-25cm.The coil consists of 5 turns, wound on a frame with a diameter 3-4mm. As a frame you can use a paste from a helium pen. For the contour, you can use a wire with a diameter of 0.5-1.2, mm (in my case, 0.8 mm). The microphone can take almost any electronic one, sensitivity is not very important, because the bug has an additional microphone amplifier. The whole installation was done on a breadboard, because it did not want to poison the board for the bug, the efficiency of which is not yet clear. Resistors are soldered from the back of the board.To tune inthe frequency was used variable capacitor, which, after full adjustment was replaced by a constant (capacity 18 picofarad). By rotating this capacitor, you can tune the bug to the frequency you need. The beetle works at frequencies of 96-99 MHz, it can be caught on a regular FM receiver. With a quality receiver, the bug can be caught at a distance of up to 150 meters.
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